Prostate cancer is common in man yet new and effective treatment options are limited. The challenge of contemporary cancer research is elucidate new factors, which if blocked, could block tumor progression. MiRs are novel candidates for these new target molecules. The purpose of this grant application is to identify and validate miRs that control prostate tumorigenicity and metastasis. Such miRs are useful biomarkers not only to identify alterations leading to disease, but targets or drugs to block tumor progression. Since miRs display tissue-specific expression patterns and target hundreds of mRNAs, changes in miR expression could alter numerous downstream events. MiR array screens have been done on whole prostate tumors, which have generated conflicting results. In part this is due to the failure to consider that prostate tumors are heterogeneous and contain many different cell-types and tumor cells at various stages of disease progression. Whole tumor screens make it difficult to determine which miRs are truly regulating disease progression. The function of many proposed tumor suppressor miRs or oncomiRs has NOT been verified by experimentation. To address this issue we are using Laser Capture Microdissection (LCM) of Formalin-Fixed Paraffin Embedded (FFPE) or frozen biopsy sections of human prostate tumors to determine which miRs are differentially expressed in actual tumor cells and could be causative to disease progression. By this approach we have verified that miR-17-3p functions in vitro and in vivo as a prostate tumor suppressor and targets the protein, vimentin. Aim 1 will define the impact of miR17-3p to orthoptopic tumorigenicty and metastasis, and elucidate additional miR17-3p targets. Using a combination of bioinformatics and biochemical approaches we have preliminary data that IGF-1R is targeted by miR17-3p. Aim 2 will identify and experimentally validate other tumor suppressor miRs and oncomiRs that control tumor progression. LCM analysis of FFPE or frozen biopsy samples will define miRs that are differentially expressed in stroma, benign glandular epithelium, PNI, and high-grade PIN as a prelude to neoplasia. Analysis of tumor cells of different pathologic stages (T2-T3/T4) and Gleason patterns (G3-G5) will determine which miRs are differentially expressed as tumors become more aggressive. The role of these putative tumor suppressor miRs or oncomiRs will be validated by stably altering miR expression in appropriate prostate cell lines followed by monitoring the subsequent effect on cell behavior in vitro and tumor growth in vivo in male, athymic nude mice. These efforts will identify oncomiRs, which promote tumorigenicity, and tumor suppressor miRs, which suppress tumorigenicity, thereby affecting prostate cancer cell behavior. In addition to expanding our understanding of the role of specific miRs in prostate cancer progression, this study has high potential to identify biomarkers that contribute to metastatic disease and offer new therapeutic agents to combat prostatic carcinoma.